14 research outputs found

    Experimental Study on the Damage and Failure Characteristics of High-Temperature Granite after Liquid-Nitrogen Cooling

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    To analyze the influence of liquid-nitrogen cooling on the damage and failure of high-temperature granite, granite samples were heated to 150~600 °C for natural cooling and liquid-nitrogen cooling treatment. Brazilian splitting tests were carried out as the samples returned to room temperature, and basic tensile and energy evolution parameters were obtained. Acoustic emission signal parameters during loading were recorded. The experimental results showed that the heating process caused damage to the granite samples, and liquid-nitrogen cooling further increased the degree of damage. Specifically, the ultrasonic velocity of liquid-nitrogen-cooled samples was lower than that of naturally cooled samples at each heating temperature. With an increase in heating temperature, the AE ring-down counts of liquid-nitrogen-cooled samples were higher than that of naturally cooled samples. At the same heating temperature, the dissipated energy of naturally cooled samples was greater than that of liquid-nitrogen-cooled samples. Liquid-nitrogen cooling could effectively promote the propagation of microcracks inside high-temperature granite and result in a reduction in the mechanical strength of granite, which could be conducive to the efficient fracture of high-temperature rock during fracturing

    Experimental study on the breakdown mechanism of high temperature granite induced by liquid nitrogen fracturing: An implication to geothermal reservoirs

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    To reveal the breakdown mechanism of dry hot rock (HDR) induced by liquid nitrogen (LN) fracturing, the laboratory tests were performed on high temperature granite using specialized apparatus. The breakdown pressure and fracture morphology of high temperature granites subjected to different heating temperatures and thermal treatments were analyzed. The results showed that the breakdown pressure of granite decreased with heating temperature increasing. As the heating temperature increased from 25 °C to 300 °C, the breakdown pressure of high temperature granite decreased by 40.63%. In addition, the failure mode mainly presented in the form of tensile fractures, which developed into bi-wing fractures along the hole axis. For heating temperature higher than 220 °C, the high temperature granite presented an increase in fracture complexity with the increased heating temperature. After pre-cooled with LN, the breakdown pressure was lowered and the fracture complexity was enhanced. For example, the breakdown pressure of LN-treated sample was 4.61%–27.70% lower than heated sample. Under cryogenic conditions induced by LN, the failure mode mainly presented in the form of randomly distributed tiny cracks and holes, which made the breakdown pressure decreased by 8.67%–59.46%. LN fracturing could cause multiple cracking effects including thermal fracturing (i.e., thermal shock, cryogenic damage and cryogenic cracking) and pressure-induced fracturing on HDR. Importantly, the thermal fracturing effect could reduce the breakdown pressure and improve the fracture complexity

    Neoadjuvant Efficacy of Three Targeted Therapy Strategies for HER2-Positive Breast Cancer Based on the Same Chemotherapy Regimen

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    (1) Background: The objective of our study was to provide evidence for choosing the optimal neoadjuvant therapy strategies for patients with human epidermal growth factor receptor 2 (HER2)-positive early breast cancer. Three neoadjuvant targeted therapy strategies (H + Py, trastuzumab plus pyrotinib; H, trastuzumab; HP, trastuzumab plus pertuzumab) based on the same chemotherapy regimen (TC, docetaxel and carboplatin) were included in the present study; (2) Methods: We retrospectively analyzed patients with HER2-positive breast cancer who were treated with neoadjuvant TCH + Py, TCH or TCHP, followed by surgery. The outcome was the pathological complete response (pCR) rate; (3) Results: In total, 545 patients were enrolled. The pCR rate was 55.6% (35/63) in the TCH + Py cohort, 32.7% (93/284) in the TCH cohort, and 56.6% (112/198) in the TCHP cohort. The multivariate analysis showed that patients who received TCH had less possibility to achieve pCR than those who received TCH + Py (odds ratio (OR) = 0.334, 95% confidence interval (CI): 0.181–0.619, p < 0.001), while patients who received TCHP had comparable possibility to those who received TCH + Py (OR = 1.043, 95%CI: 0.554–1.964, p = 0.896); (4) Conclusions: TCH + Py provides a better pCR rate compared with TCH, and a comparable pCR rate with TCHP among patients with HER2-positive breast cancer in the neoadjuvant setting. The present study supports a novel potential treatment option for these patients. Further studies need to be explored in the future

    The Modelling of Freezing Process in Saturated Soil Based on the Thermal-Hydro-Mechanical Multi-Physics Field Coupling Theory

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    The freezing process of saturated soil is studied under the condition of water replenishment. The process of soil freezing was simulated based on the theory of the energy and mass conservation equations and the equation of mechanical equilibrium. The accuracy of the model was verified by comparison with the experimental results of soil freezing. One-side freezing of a saturated 10-cm-high soil column in an open system with different parameters was simulated, and the effects of the initial void ratio, hydraulic conductivity, and thermal conductivity of soil particles on soil frost heave, freezing depth, and ice lenses distribution during soil freezing were explored. During the freezing process, water migrates from the warm end to the frozen fringe under the actions of the temperature gradient and pore pressure. During the initial period of freezing, the frozen front quickly moves downward, the freezing depth is about 5 cm after freezing for 30 h, and the final freezing depth remains about 6 cm. The freezing depth of the soil column is affected by soil porosity and thermal conductivity, but the final freezing depth mainly depends on the temperatures of the top and lower surfaces. The frost heave is mainly related to the amount of water migration. The relationship between the amount of frost heave and the hydraulic conductivity is positively correlated, and the thickness of the stable ice lens is greatly affected by the hydraulic conductivity. With the increase of the hydraulic conductivity and initial void ratio, the formation of ice lenses in the soil become easier. With the increase of the initial void ratio and thermal conductivity of soil particles, the frost heave of the soil column also increases. With high-thermal-conductivity soil, the formation of ice lenses become difficult

    Microwave-Assisted Dip Coating of Aloe Vera on Metallocene Polyethylene Incorporated with Nano-Rods of Hydroxyapaptite for Bone Tissue Engineering

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    Bone tissue engineering widely explores the use of ceramic reinforced polymer-matrix composites. Among the various widely-used ceramic reinforcements, hydroxyapatite is an undisputed choice due to its inherent osteoconductive nature. In this study, a novel nanocomposite comprising metallocene polyethylene (mPE) incorporated with nano-hydroxyapaptite nanorods (mPE-nHA) was synthesized and dip coated with Aloe vera after subjecting it to microwave treatment. The samples were characterized using contact angle, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscopy (AFM) and 3D Hirox microscopy scanning. Contact angle results show that the hydrophilicity of mPE-nHA improved notably with the coating of Aloe vera. The surface topology and increase in surface roughness were observed using the SEM, AFM and 3D Hirox microscopy. Blood compatibility assays of pure mPE and the Aloe vera coated nanocomposite were performed. The prothrombin time (PT) was delayed by 1.06% for 24 h Aloe-vera-treated mPE-nHA compared to the pristine mPE-nHA. Similarly, the 24 h Aloe-vera-coated mPE-nHA nanocomposite prolonged the activated partial thromboplastin time (APTT) by 41 s against the control of pristine mPE-nHA. The hemolysis percentage was also found to be the least for the 24 h Aloe-vera-treated mPE-nHA which was only 0.2449% compared to the pristine mPE-nHA, which was 2.188%. To conclude, this novel hydroxyapatite-reinforced, Aloe-vera-coated mPE with a better mechanical and anti-thrombogenic nature may hold a great potential to be exploited for bone tissue engineering applications

    Diffuse scattering from dodecagonal quasicrystals

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    General formulae for thermal diffuse scattering from quasicrystals are applied to the case of dodecagonal quasicrystals from corresponding elasticity theory. Contours of constant diffuse scattering intensity are illustrated. Unlike ordinary crystals, shapes of isointensity contours are much more complicated and vary even among the collinear Bragg spots. Diffuse scattering patterns in the plane perpendicular to a given zone axis are associated with corresponding specific elastic constants. Information about elastic constants can be extracted from quantitative analysis of diffuse scattering patterns
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